Electrical tools using a bit, driven by impact, are generally known. Since such tools subject a bit to high frequency impacts during operation, there is a higher requirement for the toughness of the bit. A traditional bit is formed from a single metal, thus the hardness of the bit from front end to back end is consistent. Generally, the requirement for the toughness is sacrificed for meeting the requirements for wear resistance and durability. Once the hardness is reduced to enhance the toughness, the wear resistance and durability may be reduced greatly, and even lower than the standard requirement, thus cannot be satisfactory.